18 The Pacific Plate through Geologic Time

Tuesday, 23 May 2017
1:30 PM - 4:50 PM
Room 319A

LINKING THE HISTORY OF THE HAWAIIAN HOTSPOT MOTION TO PACIFIC PLATE EVOLUTION AND DEEP MANTLE PROCESSES: NEW PALEOMAGNETIC DATA FROM MIDWAY ATOLL (~27 MA)

Paper number: 18-4
Program: Theme Sessions
Time: 2:15 PM – 2:35 PM

Authors

Abstract

The bend in Emperor seamounts formed by the Hawaiian hotspot ~47 Ma poses a challenge in the construction of Pacific plate motion models. Paleomagnetic studies and mantle convection models allow for insight in the absolute plate motion history. However, plate circuit models are unable to accurately predict the trace of the Hawaiian hotspot prior to the bend, suggesting there is an unaccounted for source of hotspot motion. Paleomagnetic studies of basalt cores recovered by ocean drilling of the Emperor seamounts during ODP Leg 197 (Tarduno et al., Science, 2003) preserve the best record of Hawaiian hotspot motion of >40 mm/yr. These data suggest that the great Hawaiian-Emperor bend (HEB) records primarily a change in mantle plume motion (Tarduno et al., Science, 2009). Furthermore, mantle convection models (Hassan et al., Nature, 2016) reproduce deep mantle plume motion consistent with the formation of the HEB. A fixed hotspot model is inconsistent with data used for Pacific "absolute plate motion models" for times prior to the HEB; currently, plate circuit derived predictions are the most reliable estimate of Pacific absolute plate motion prior to the HEB (e.g., Doubrovine and Tarduno, JGR, 2008). Since the HEB, a small discrepancy persists between the plate circuit model predicted hotspot track and the observed seamount trace until ~10 Ma. This offset may record further motion of the Hawaiian hotspot since the HEB. Alternatively it may contain a small signal of motion between Pacific and Indo-Atlantic hotspot groups. New paleomagnetic data from Midway Atoll (~27 Ma) suggests that the paleolatitude for the Hawaiian hotspot is similar to its current position (Bono, dissertation, 2016). We note that this indicates purported paleolatitudes suggested from marine magnetic anomaly data (Horner-Johnson and Gordon, JGR, 2010) are far more uncertain than claimed, and that interpretations of true polar wander based on these data are mistaken. The new data from Midway suggest motion between Atlantic and Pacific hotspot groups, potentially placing a bound on the fixity of their associated deep mantle underpinnings (the African and Pacific Large Low Shear Velocity Provinces).

Geological Society of America Abstracts with Programs. Vol. 49, No. 4

doi: 10.1130/abs/2017CD-292896

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